Thursday, December 8, 2011

Single Transistor LED Flasher Circuit

Posted by
hitman

Can you imagine of making a formidable little LED flasher or blinker using just a single transistor and a couple of other passive parts.
That looks too good to be tue, however the following diagram will simply prove that it's really possible to create a legal LED blinker using just one general purpose transistor as the main component.

I came across this phenomena some eight years ago, accidentally, while trying to make a smallest possible motorcycle side indicator flasher, and was really amazed.
However, then I did have not any idea that it was happening due to the negative resistance characteristics of the transistor.

The circuit actually exploits the negative resistance factor in transistors to produce the blinking effect.

I'll be soon writing a comprehensive article on this and we'll see there how the concept can be modified in many different ways.

57 comments:

I actually wanted a circuit of water flow controller which will be fitted in the overhead tank only. When the level of water in this overhead tank goes below a certain level, the pump is switched on and it starts pumping water from the underground tank; when the overhead tank is full, it is switched off; plus motor protection in case there is no water in the underground tank. my email id is sanjay8040@gmail.comthanks

As i understand, the circuit in Bright Hub is of a level indicator and motor protector , to be installed in the overhead tank; the water level controller is to be installed in the underground tank. Now I want a controller cum motor protector which can be installed in the overhead tank itself. Our underground tank is very big so it may not be practical to put the controller there. Thanks

Hi Sunjay,You can install the entire circuit in your overhead tank, only the points at "F" needs to be positioned in such a way that it comes in contact with the water that's entering the motor.Thus, as long as water supply is present to the motor, it remains switched ON and the moment water supply stops, the motor also stops.

I shud use the last circuit meant for the overhead tank, with IC 4049. When water level reaches point A, the motor will stop; and when water level goes below point E, motor will start. My doubt was that at point E, there are only 2 points from the IC. Will this work to start the motor? I hope my understanding is correct. Thanks a lot for your guidance. Regards

The ground point shown at the bottom, inside the tank is the common point for all the sensing terminals, it must be immersed in the water at the bottom of the tank permanently.Here the motor does not have any connections with the sensors in the upper tank.The motor will switch ON and OFF depending upon the water supply present to it, as long as there's water entering it, it remains switched ON, as soon as water supply ends, the motor stops, this is the only way through which we can protect the motor.In simple words as long as water is present across point F, the motors is switched ON and vice versa.So you can position this point anyway you want, whether in the upper tank or in the underground tank, it will depend on you how you want to switch the motor.Regards.

hi swagatam..thanks for your quick reply. Since our underground tank is very big, the OHT will start overflowing with the system in question. I am looking for a system similar to the one for the UGT. Actually it will be reverse of the UGT system. At C, the motor starts and at A, the motor stops. And if u can provide F type protection, all the more better. I hope i am able to make myself clear. Best regards.

OK, it means you require motor control from both the tanks, it can be done simply by introducing the point F near the brim of the OHT.May be today or by tomorrow I'll be posting a new article on this subject, I'll post the diagram there and inform you. You can check it once it gets published.Regards.

hi swagatam..ref ur msg of 14th..i was waiting for the circuit diagram of the water level 'CONTROLLER' for the overhead tank. The circuit given by you for tha OHT in Bright Hub, as i understand, is that of a level indicator. Thanks n regards

Hi Sunjay,If you want a circuit only for controlling the motor pump, then you may refer the following diagram.http://homemadecircuitsandschematics.blogspot.com/2011/12/how-to-make-simple-water-level.html

I am trying to imitate cloud to cloud lightning using the smallest possible circuit. I found this project that uses only the flashing LEDs and a battery...http://www.youtube.com/watch?v=Rj5tqhGypAE&feature=player_embedded. I found 3mm flashing LEDs ...http://lighthouseleds.com/led-component-lighting/animated-leds-flashing-blinking/3mm-led-flashing-round-top.htmlCan I power 2-3 of these (amber and/or white) using one CR2032 battery? Can I get them to flash at different rates? ...I think that may drain the battery too quickly since there are no resisitors used, is that correct?

I am trying to imitate cloud to cloud lightning using the smallest possible circuit. I found this project that uses only the flashing LEDs and a battery (Candle Flicker Hair Bow). I found 3mm flashing LEDs (3-3.4V, 20mA, 1 Hz flash frequency)Can I power 2-3 of these (amber and/or white) using one CR2032 battery? Can I get them to flash at different rates? ...I think that may drain the battery too quickly since there are no resisitors used, is that correct?

I want to design a LED Flasher Cirrcuit with Input : 9V-16V, On time : 0.5s +/- 10%, Period : 1s +/- 10%, Reverse polarity protection : required can you help me with the above circuit? Will it work for this conditions?need your response thank you

thanks for your prompt response.Could you Just modify the circuit for this specifications LED Flasher Circuit with Input : 9V-16V, On time : 0.5s +/- 10%, Period : 1s +/- 10%, Reverse polarity protection required, by using any other stage of RC or any other way. Using astable multivibrators is cost effective for my project, need a simple circuit. Hope for your response.

In the circuit, the capacitor is charged by R1 until the voltage becomes large enough to get the emitter-base junction to avalanche which lights up the LED and also discharges the capacitor to trigger a fresh cycle....it basically takes place due to the negative resistance characteristic of the BJT

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About Me

I am an electronic hobbyist, inventor, a freelance electronic circuit designer, manufacturer. I am also an avid publisher, I enjoy posting electronic related articles in my website: http://www.homemade-circuits.com/ where the interested viewers get the opportunity to read about many innovative electronic circuit ideas, exclusively designed and developed by me.